In the art of concrete construction, it is commonplace to form "cold joints" between two or more poured concrete slabs. Such cold joints frequently become uneven or buckled due to normal thermal expansion and contraction of the concrete and/or compaction of the underlying soil caused by inadequate substrate preparation prior to pouring of the concrete. As a means of preventing buckling or angular displacement of such cold joints, it is common practice to insert smooth steel dowel rods generally known as "slip dowels" within the edge portions of adjoining concrete slabs in such a manner that the concrete slabs may slide freely along one or more of the slip dowels, thereby permitting linear expansion and contraction of the slabs while at the same time maintaining the slabs in a common plane and thus preventing undesirable bucking or unevenness of the cold joint.
In order to function effectively, slip dowels must be accurately positioned parallel within the adjoining concrete slabs. The non-parallel positioning of the dowels will prevent the desired slippage of the dowels and will defeat the purpose of the "slip dowel" application. Additionally, the individual dowels must be placed within one or both of the slabs in such a manner as to permit continual slippage or movement of the dowels within the cured concrete slab(s).
In the prior art, two methods of installing smooth "slip dowels" have become popular. According to the first method, a first concrete pour is made within a pre-existing form. After the first pour has cured, an edge of the form (usually a wooden stud) is stripped away. A series of holes are then drilled parallel into the first pour along the exposed edge from which the form has been removed. The depth and diameter of the individual holes varies depending on the application and the relative size of the concrete slabs to be supported. As a general rule, however, such holes are at least 12 inches deep and typically have a diameter of approximately five-eighths of an inch.
After the parallel aligned series of holes has been drilled into the first pour, smooth dowel rods are advanced into each such hole such that one end of each dowel rod is positioned within the first pour and the remainder of each dowel rod extends into a neighboring area where a second slab of concrete is to be poured. Thereafter, concrete is poured into such neighboring area and is permitted to set with the parallel aligned dowels extending thereinto. After the second pour has set, the slip dowels will be held firmly within the second slab but will be permitted to slide longitudinally within the drilled holes of the first slab thereby accommodating longitudinal expansion and contraction of the two slabs while at the same time preventing buckling or angular movement therebetween.
Although the above described "drilling method" of placing slip dowels has become popular, it will be appreciated that such method is extremely labor intensive. In fact, it takes approximately ten minutes to drill a five-eighths inch diameter by twelve inches long hole into the first pour, and the drilling equipment, bits, accessories, and associated set up time tends to be very expensive. Moreover, the laborers who drill the holes and place the slip dowels must be adequately trained to insure that the dowels are arranged perpendicular to the joint but parallel to one another so as to permit the desired slippage during subsequent use.
The second popular method of placing slip dowels involves the use of wax treated cardboard sleeves positioned over one end of each individual dowel. According to such method, a series of holes are drilled through one edge of a concrete form and smooth dowels are advanced through each such hole. Wax treated cardboard sleeves are placed over one end of each dowel and the first pour is made within the form. After the first pour has set, the previously drilled form is stripped away leaving the individual dowels extending into a neighboring open space where the second pour is to be made. Subsequently, the second pour is made and permitted to cure. Thereafter, the slip dowels will be firmly held by the concrete of the second pour but will be permitted to longitudinally slide against the inner surfaces of the wax treated cardboard sleeves within the first pour. Thus, the waxed cardboard sleeves facilitate longitudinal slippage of the dowels, while at the same time holding the two concrete slabs in a common plane, and preventing undesirable buckling or angular movement thereof.
This second method, while presently popular, is nonetheless associated with numerous deficiencies. For example, after the first pour has been made, the free ends of the dowels are likely to project as much as eighteen inches through the forms and into the open space allowed for the second pour. Because the drilled section of form must be advanced over those exposed sections of dowel to accomplish stripping or removal of the form, it is not infrequent for the exposed portions of the dowels to become bent and, thus, nonparallel. Also, the drilled section of form may become damaged or broken during the removal process, thereby precluding its reuse.
It is unfortunate that both of the above-described popular methods of placing slip dowels often result in the dowels being finally positioned at various angles rather than in the desired parallel array. When such occurs, the necessary slippage of the dowels is impeded or prevented.
There is also known in the prior art dowel placement devices which comprise elongate, hollow tubes sized to receive portions of the dowel rods. The tubes are mounted to one edge of the concrete form in generally parallel relation to each other via integral base portions, with a first pour being made thereabout. After the first pour has cured, the edge of the concrete form to which the tubes are mounted is stripped away from the first slab, with dowel rods being advanced into the exposed open ends of the tubes embedded within the first slab. Those portions of the dowel rods not advanced into the tubes extend into a neighboring area where a second pour of concrete is to be made. The pouring of the concrete into the neighboring area encapsulates the dowel rods which are held firmly within the second slab formed by the curing of the second pour. The dowels, though being firmly held within the second slab, are permitted to slide longitudinally within the tubes embedded in the first slab.
Though the use of these prior art placement devices presents advantages over the previously described placement methods, these devices also possess certain deficiencies which detract from their overall utility. In particular, the attachment of the base portions of these prior art placement devices to a concrete form often requires the use of multiple fasteners, which makes the attachment process a difficult and time-consuming task. Additionally, in the prior art placement devices both the tube and its integral base portion used to facilitate the connection of the tube to the concrete form are embedded in the first slab, thus necessitating that additional placement devices be attached to the concrete form prior to its reuse.
Accordingly, there remains a need in the art for methods and/or devices for facilitating the proper placement of slip dowels which overcome the previously described deficiencies associated with prior art placement devices.